The present invention relates generally to image data processing and, more particularly, to improvements in methods of producing enhanced image data by data processing and to a recording medium carrying such image data.
It is common practice in the prior art that images produced on a television receiver, a monitor or a CRT display of a home video-game machine, a microcomputer, or a graphic computer are substantially two-dimensional. Such images are usually animated by moving and varying a two-dimensional character or object on a planar two-dimensional background. However, such two-dimensional images or pictures are limited in both the modeling of a background and the movement of character objects, thus failing to yield more realistic images, particularly in a video game.
For improvement, various methods of making highly realistic three-dimensional images or pictures have been proposed and some of them are described below. One of various predetermined movements of a character object viewed from several directions may be selected and displayed according to visual variation, such as a change in the viewpoint in the image. Also, a simulated three-dimensional image may be created by overlapping a plurality of two-dimensional graphics, one over the other, in a depthwise direction. A texture mapping method may also be provided in which the surfaces of a polygon are filled with a texture map (of material or pattern) to generate an image model. In another method, a variation of colors is produced by changing color data of the image with the use of a color lookup table.
In a typical example of a prior art home video-game machine, manipulation information is introduced from an input device, such as an entry pad or a joy stick, and is passed across an interface along a main bus by the action of a CPU consisting mainly of a microprocessor. Upon introduction of the manipulation data, three-dimensional data stored in a main memory is transmitted by the action of a video processor to a source video memory for temporary storage.
The aforementioned CPU also operates to transfer to the video processor a specific sequence for reading out a series of image data segments from the source video memory for overlapping them, one over the other, on the screen. According to the reading sequence of the image data segments, the video processor reads the image data segments from the source video memory and displays them in their overlapped arrangement.
While the image data segments are being read and displayed, audio components of the manipulation information are fed to an audio processor which, in turn, picks up corresponding audio data from an audio memory for synchronization with the image data.
For example, the source video memory may hold a background of a checker-board pattern and a group of rectangular image segments or sprites representing cross sections of a cylindrical object in the background. Other areas besides the cross sections of the cylindrical object on the sprites may be drawn in transparency.
A sync generator mounted in the video processor generates a read address signal in response to a sync signal of the image data. The read address signal of the sync generator is transmitted via the main bus to a read address table determined by the CPU. The sync generator also reads the image segments from the source video memory in response to a signal from the read address table.
The video data segments retrieved are then fed to an overlap processor where they are overlapped, one over the other, in the sequence determined by a priority table and passed via the main bus from the CPU. Since the background comes the first and is then followed by the rectangle sprites, the group of sprites being placed in superposition, one over the other, on the background.
Then, the other areas in addition to the cross sections of the cylindrical object of the aforementioned sprites, which are overlapped one over the other on the background, are rendered to transparency by a suitable transparency processor. As a result, the two-dimensional image data of the cylindrical object can be reproduced as three-dimensional data VDO of the original image.
The CPU delivers various fundamental commands for color assignment using color lookup tables and texture mapping, application of a semitransparency process for providing a semitransparent state by mixing the pixel data (including R, G, and B color component data) of the current image being displayed with the pixel data of a succeeding image at a specific ratio of alpha, and application of a dithering process by switching on and off its action where the boundary between two colors is smoothed by noise. However, due to assignment of a range of textures and color lookup tables, the semitransparency process, and the dithering process, their commands should be increased in word length. Moreover, amounts of data to be stored in the source video memory will be increased accordingly.
For example, the semitransparency process is carried out in the transparency processor of the video processor by mixing the pixel data of the current image being displayed with the pixel data of a succeeding image at the alpha mixture ratio determined and supplied by the CPU. In a conventional manner of the semitransparency process, the alpha mixture ratio is carried in a drawing command and, thus, is stored in the source video memory for every pixel. If it is desired that the mixture ratio hold more setting details, the number of bits assigned to the ratio must be increased. Consequently, the prior art drawing command is substantially increased in data length and will occupy considerable storage area in the source video memory.
Accordingly, there has been a long existing need for enhanced image data processing having reduced word length and memory storage requirements. The present invention clearly fulfills these needs.